How to Kill Quackgrass

Weeds like quackgrass require sustained efforts in order to eradicate them.

Quackgrass (Elytrigia repens) is a cool-season perennial grass that invades lawns and gardens and can steal vital nutrients and moisture from desirable plants. Quackgrass grows 1 to 4 feet tall, with stalks that look like miniature wheat. The weed spreads via creeping rootstocks, and new plants can grow from pieces of old roots left in the ground. Rhizomes can lurk 6 to 8 feet under the surface of the soil and eventually erupt into new plants, making quackgrass extremely difficult to eradicate. Quackgrass may eventually return despite your best efforts to control it. A non-native plant, quackgrass grows in almost any soil and can even sprout in gravel.

Non-Selective Herbicide

One way to kill quackgrass is to squirt each clump with glyphosate herbicide. This systemic herbicide is non-selective, which means it kills any plant it touches, so use it carefully. Do not spray glyphosate on a windy day, or when rain may fall within 48 hours. If the quackgrass is too close to desirable plants to spray it, you can "paint" the weed's leaves with glyphosate herbicide using a small paintbrush. The herbicide is absorbed into the weed's circulatory system, killing it down to the roots. For large fields of quackgrass with no desirable plants close by, a pump or backpack sprayer can help the job go faster. A little glyphosate goes a long way; it is not necessary to drench the quackgrass. More than one application may be necessary, since many of the rhizomes underground will have dormant buds. Try applying nitrogen fertilizer to break the dormancy before applying glyphosate herbicide. Read product labels carefully, as some ingredients mixed with the glyphosate may be harmful.

Selective Herbicide

Selective herbicides work systemically to kill the quackgrass from the inside out. Look for herbicides containing fluazifop. Wait until the weather forecast calls for no rain for at least 48 hours and carefully apply the herbicide to the leaves of the quackgrass. Apply the herbicide when the quackgrass is very young, with only two to four leaves. A second application may be necessary. Follow label directions.

Organic Methods

Spread a thick layer of mulch over the quackgrass to smother it. This can kill the plant you target, but those pesky rhizomes will still dig around underneath the soil until they find a clear spot to emerge. Planting a cover crop can also smother quackgrass. Plant winter rye, barley, clover, beans, crown vetch or buckwheat, rotating to a different crop each time. Till each mature crop back into the soil for a bonus: the crops add nutrients to the soil after tilling. (Please note that crown vetch is considered invasive in some areas of the country; check with your local cooperative extension before planting it.) Use the lawn mower to repeatedly slice the quackgrass blades as close to the soil as possible to deprive them of optimum photosynthesis. The rhizomes will die eventually. You can also dig up the rhizones by hand. Toss them someplace to dry out, then dispose of them. If the quackgrass is infesting the lawn, try adding more nitrogen fertilizer to help the grass choke out the quackgrass. Use 1/4 to 1/2 pound of nitrogen per 1,000 square feet of lawn every two weeks while the grass is actively growing, and mow the lawn frequently. By the following year, you should see fewer and smaller patches of quackgrass.

Mechanical Methods

In addition to digging up the rhizomes by hand, you can try baking the plants to death. This method, called solarization, requires plenty of sunlight and warmth. Spread clear plastic over the quackgrass, plus a few inches beyond it. Fasten or weight the plastic down. The temperature beneath the plastic will rise significantly, killing off the quackgrass. After several days, you should be able to rake up the dead quackgrass. Till larger colonies of quackgrass during the hottest, sunniest, dryest weather possible. The tilling must be done repeatedly, before any new quackgrass sprouts develop three leaves. Every time the quackgrass is tilled, it expends energy and nutrients to produce new sprouts. Repeated tillage eventually exhausts the plant's food supply. Eradicating quackgrass by this method can take up to two years.

Prevention

While quackgrass seed may be dispersed by the wind and rhizomes may hide underground, there are some steps you can take to avoid inadvertently introducing quackgrass to your garden. The University of Iowa extension service website recommends buying only high-quality garden seeds from reputable sources. Avoid using straw mulch or livestock feed that may be infested with quackgrass. Keep the area around the garden mowed and make sure clippings that may contain quackgrass seeds blow away from the garden. Do not use grass clippings for mulch if there is quackgrass in the lawn.

About the Author

Audrey Lynn has been a journalist and writer since 1974. She edited a weekly home-and-garden tabloid for her hometown newspaper and has regularly contributed to weekly and daily newspapers, as well as "Law and Order" magazine. A Hambidge Fellow, Lynn studied English at Columbus State University.